The present invention is directed to cutting tools for producing gears and other toothed articles. In particular, the present invention relates to a method of grinding cutting tools.
Grinding of cutting blade blanks or cutting blades is usually performed when initially producing desired surfaces and/or edges on a cutting blade blank to form a cutting blade, or, when a worn cutting blade is ground (sharpened) to restore surfaces and/or edges to their original condition.
In the manufacture of gears and other toothed articles, especially bevel and hypoid gears, it is common to employ cutting blades known as xe2x80x9cstick-typexe2x80x9d cutting blades usually formed from a length of bar stock material, for example, high speed steel (HSS) or carbide.
Predominantly, there are two styles of stick-type cutting blades. There are those cutting blades that when sharpened require only two side profile surfaces (pressure angle side and clearance side) to be ground in order to restore the respective cutting and clearance edges of the blades. Examples of such blades can be seen in U.S. Pat. No. 4,575,285 to Blakesley, U.S. Pat. No. 6,004,078 to Clark et al. or U.S. Pat. No. 6,120,217 to Stadtfeld et al.
The other style commonly found are those cutting blades that in addition to grinding the two side profile surfaces also requires grinding of the front face of the cutting blade in order to restore cutting and clearance edges. An example of these cutting blades can be found in U.S. Pat. No. 4,183,182 to Kotthaus.
In grinding either of the above types of cutting blades there are generally two methods employed, form grinding and generating grinding. In form grinding, a grinding wheel has a desired blade geometry dressed into the wheel. Plunging the grinding wheel against the cutting blade imparts the dressed form onto the cutting blade. Examples of this type of grinding can be seen in U.S. Pat. No. 4,144,678 to Ellwanger et al., U.S. Pat. No. 3,881,889 to Hunkeler or previously mentioned U.S. Pat. No. 4,183,182. With processes such as those above, a large area of contact exists which may result in significant heat build-up leading to burning of the tool and/or rapid degradation of the grinding wheel especially if aggressive grinding practices are followed (i.e. rapid rate of stock removal or a large amount of stock material removed per pass of the grinding wheel).
In generating grinding, a grinding wheel having a simple profile form is utilized to grind cutting blades. Relative motion between the grinding profile surface and the cutting tool result in the desired geometry being generated on the cutting tool. Examples of generating processes carried out by cup-shaped grinding wheels having a roughing section and a simple profile form section for finish grinding can be found in U.S. Pat. No. 5,168,661 to Pedersen et al. or U.S. Pat. No. 5,480,343 to Pedersen et al. In these types of processes, the finish profile form also represents a significant total area of contact with the cutting blade thus again presenting not only the risk of burning of the cutting blade and degradation of the grinding wheel but also exhibiting significant wear. Since the simple profile form is utilized for finishing operations, aggressive grinding practices may be damaging to the grinding wheel and/or cutting blade and frequent dressing of the finish profile form is required to restore the worn surface in order to maintain an acceptable profile form.
U.S. Pat. No. 4,488,381 to Konersmann teaches a method of grinding cutting blades utilizing a grinding disk that is traversed along a surface of a grinding wheel and which employs the circular edge of the grinding disk to remove material from the cutting blade. Only one grinding edge of the grinding disk is utilized for grinding and when the grinding disk becomes worn, the grinding disk is moved laterally to bring the grinding disk closer to a cutting tool such that sufficient abrasive action may again take place.
The present invention comprises a method of grinding cutting blades with a grinding wheel having first and second grinding edges. The method comprises rough grinding at least one surface of the cutting blade with the first grinding edge and finish grinding at least one surface of the cutting blade with the second grinding edge.
The present invention also includes a method of forming primary and secondary relief surfaces on the cutting profile surface of a cutting blade. The primary relief surface extends from the cutting edge to a location inward of the cutting edge and is oriented according to the nominal cutting relief angle specified for that particular side of the cutting blade. The secondary relief surface extends from the inward edge of the primary relief surface to the back face of the blade. The secondary relief surface is oriented with a relief angle equal to or greater than the nominal relief angle required for that side of the cutting blade.